......

a. $\frac{-3}{4}$ + $\frac{2}{7}$ + $\frac{-1}{4}$  + $\frac{3}{5}$ + $\frac{5}{7}$ = $\frac{-3-1}{4}$  + $\frac{2+5}{7}$  + $\frac{3}{5}$ = $\frac{-4}{4}$  $\frac{7}{7}$ + $\frac{3}{5}$ = -1 + 1 + $\frac{3}{5}$ = $\frac{3}{5}$ 

b. $\frac{6}{21}$ - $\frac{-12}{44}$ + $\frac{10}{40}$ - $\frac{1}{-4}$ - $\frac{18}{33}$ = $\frac{2}{7}$ + $\frac{3}{11}$ + $\frac{5}{22}$ + $\frac{1}{4}$ - $\frac{6}{11}$ 

= ($\frac{3}{11}$ - $\frac{6}{11}$ )  +  ($\frac{2}{7}$ + $\frac{1}{4}$ ) + $\frac{5}{22}$ 

= $\frac{-3}{11}$  +  ($\frac{8}{28}$ + $\frac{5}{22}$)  + $\frac{5}{22}$

= $\frac{-3}{11}$ + $\frac{15}{28}$ + $\frac{5}{22}$ = $\frac{151}{308}$

c. $\frac{-5}{8}$ - $\frac{12}{29}$ . $\frac{-8}{10}$ . 5,8 = $\frac{15}{58}$ . $\frac{-116}{25}$ = $\frac{-6}{5}$

@nhw2903      #HĐ247 

Câu D mình chỉ biết đáp án là $\frac{19}{9}$ thôi ạ. Bạn tự tìm hiểu nha.